Merge branch 'cr/push-force-tag-update'

Require "-f" for push to update a tag, even if it is a fast-forward.

* cr/push-force-tag-update:
  push: allow already-exists advice to be disabled
  push: rename config variable for more general use
  push: cleanup push rules comment
  push: clarify rejection of update to non-commit-ish
  push: require force for annotated tags
  push: require force for refs under refs/tags/
  push: flag updates that require force
  push: keep track of "update" state separately
  push: add advice for rejected tag reference
  push: return reject reasons as a bitset

13 files changed, 188 insertions, 60 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index bf8f911e1..50a228899 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -140,10 +140,11 @@ advice.*::
 	can tell Git that you do not need help by setting these to 'false':
 +
 --
-	pushNonFastForward::
+	pushUpdateRejected::
 		Set this variable to 'false' if you want to disable
-		'pushNonFFCurrent', 'pushNonFFDefault', and
-		'pushNonFFMatching' simultaneously.
+		'pushNonFFCurrent', 'pushNonFFDefault',
+		'pushNonFFMatching', and 'pushAlreadyExists'
+		simultaneously.
 	pushNonFFCurrent::
 		Advice shown when linkgit:git-push[1] fails due to a
 		non-fast-forward update to the current branch.
@@ -158,6 +159,9 @@ advice.*::
 		'matching refs' explicitly (i.e. you used ':', or
 		specified a refspec that isn't your current branch) and
 		it resulted in a non-fast-forward error.
+	pushAlreadyExists::
+		Shown when linkgit:git-push[1] rejects an update that
+		does not qualify for fast-forwarding (e.g., a tag.)
 	statusHints::
 		Show directions on how to proceed from the current
 		state in the output of linkgit:git-status[1], in
diff --git a/Documentation/git-push.txt b/Documentation/git-push.txt
index 8b637d339..c964b796b 100644
--- a/Documentation/git-push.txt
+++ b/Documentation/git-push.txt
@@ -51,10 +51,11 @@ be named. If `:`<dst> is omitted, the same ref as <src> will be
 updated.
 +
 The object referenced by <src> is used to update the <dst> reference
-on the remote side, but by default this is only allowed if the
-update can fast-forward <dst>.  By having the optional leading `+`,
-you can tell git to update the <dst> ref even when the update is not a
-fast-forward.  This does *not* attempt to merge <src> into <dst>.  See
+on the remote side.  By default this is only allowed if <dst> is not
+a tag (annotated or lightweight), and then only if it can fast-forward
+<dst>.  By having the optional leading `+`, you can tell git to update
+the <dst> ref even if it is not allowed by default (e.g., it is not a
+fast-forward.)  This does *not* attempt to merge <src> into <dst>.  See
 EXAMPLES below for details.
 +
 `tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`.
diff --git a/advice.c b/advice.c
index edfbd4a6f..d28792728 100644
--- a/advice.c
+++ b/advice.c
@@ -1,9 +1,10 @@
 #include "cache.h"
 
-int advice_push_nonfastforward = 1;
+int advice_push_update_rejected = 1;
 int advice_push_non_ff_current = 1;
 int advice_push_non_ff_default = 1;
 int advice_push_non_ff_matching = 1;
+int advice_push_already_exists = 1;
 int advice_status_hints = 1;
 int advice_commit_before_merge = 1;
 int advice_resolve_conflict = 1;
@@ -14,15 +15,19 @@ static struct {
 	const char *name;
 	int *preference;
 } advice_config[] = {
-	{ "pushnonfastforward", &advice_push_nonfastforward },
+	{ "pushupdaterejected", &advice_push_update_rejected },
 	{ "pushnonffcurrent", &advice_push_non_ff_current },
 	{ "pushnonffdefault", &advice_push_non_ff_default },
 	{ "pushnonffmatching", &advice_push_non_ff_matching },
+	{ "pushalreadyexists", &advice_push_already_exists },
 	{ "statushints", &advice_status_hints },
 	{ "commitbeforemerge", &advice_commit_before_merge },
 	{ "resolveconflict", &advice_resolve_conflict },
 	{ "implicitidentity", &advice_implicit_identity },
 	{ "detachedhead", &advice_detached_head },
+
+	/* make this an alias for backward compatibility */
+	{ "pushnonfastforward", &advice_push_update_rejected }
 };
 
 void advise(const char *advice, ...)
diff --git a/advice.h b/advice.h
index f3cdbbf29..8bf63563a 100644
--- a/advice.h
+++ b/advice.h
@@ -3,10 +3,11 @@
 
 #include "git-compat-util.h"
 
-extern int advice_push_nonfastforward;
+extern int advice_push_update_rejected;
 extern int advice_push_non_ff_current;
 extern int advice_push_non_ff_default;
 extern int advice_push_non_ff_matching;
+extern int advice_push_already_exists;
 extern int advice_status_hints;
 extern int advice_commit_before_merge;
 extern int advice_resolve_conflict;
diff --git a/builtin/push.c b/builtin/push.c
index db9ba30b0..8491e431e 100644
--- a/builtin/push.c
+++ b/builtin/push.c
@@ -220,31 +220,42 @@ static const char message_advice_checkout_pull_push[] =
 	   "(e.g. 'git pull') before pushing again.\n"
 	   "See the 'Note about fast-forwards' in 'git push --help' for details.");
 
+static const char message_advice_ref_already_exists[] =
+	N_("Updates were rejected because the destination reference already exists\n"
+	   "in the remote.");
+
 static void advise_pull_before_push(void)
 {
-	if (!advice_push_non_ff_current || !advice_push_nonfastforward)
+	if (!advice_push_non_ff_current || !advice_push_update_rejected)
 		return;
 	advise(_(message_advice_pull_before_push));
 }
 
 static void advise_use_upstream(void)
 {
-	if (!advice_push_non_ff_default || !advice_push_nonfastforward)
+	if (!advice_push_non_ff_default || !advice_push_update_rejected)
 		return;
 	advise(_(message_advice_use_upstream));
 }
 
 static void advise_checkout_pull_push(void)
 {
-	if (!advice_push_non_ff_matching || !advice_push_nonfastforward)
+	if (!advice_push_non_ff_matching || !advice_push_update_rejected)
 		return;
 	advise(_(message_advice_checkout_pull_push));
 }
 
+static void advise_ref_already_exists(void)
+{
+	if (!advice_push_already_exists || !advice_push_update_rejected)
+		return;
+	advise(_(message_advice_ref_already_exists));
+}
+
 static int push_with_options(struct transport *transport, int flags)
 {
 	int err;
-	int nonfastforward;
+	unsigned int reject_reasons;
 
 	transport_set_verbosity(transport, verbosity, progress);
 
@@ -257,7 +268,7 @@ static int push_with_options(struct transport *transport, int flags)
 	if (verbosity > 0)
 		fprintf(stderr, _("Pushing to %s\n"), transport->url);
 	err = transport_push(transport, refspec_nr, refspec, flags,
-			     &nonfastforward);
+			     &reject_reasons);
 	if (err != 0)
 		error(_("failed to push some refs to '%s'"), transport->url);
 
@@ -265,18 +276,15 @@ static int push_with_options(struct transport *transport, int flags)
 	if (!err)
 		return 0;
 
-	switch (nonfastforward) {
-	default:
-		break;
-	case NON_FF_HEAD:
+	if (reject_reasons & REJECT_NON_FF_HEAD) {
 		advise_pull_before_push();
-		break;
-	case NON_FF_OTHER:
+	} else if (reject_reasons & REJECT_NON_FF_OTHER) {
 		if (default_matching_used)
 			advise_use_upstream();
 		else
 			advise_checkout_pull_push();
-		break;
+	} else if (reject_reasons & REJECT_ALREADY_EXISTS) {
+		advise_ref_already_exists();
 	}
 
 	return 1;
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index d34201372..f849e0a4a 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -44,6 +44,11 @@ static void print_helper_status(struct ref *ref)
 			msg = "non-fast forward";
 			break;
 
+		case REF_STATUS_REJECT_ALREADY_EXISTS:
+			res = "error";
+			msg = "already exists";
+			break;
+
 		case REF_STATUS_REJECT_NODELETE:
 		case REF_STATUS_REMOTE_REJECT:
 			res = "error";
@@ -85,7 +90,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	int send_all = 0;
 	const char *receivepack = "git-receive-pack";
 	int flags;
-	int nonfastforward = 0;
+	unsigned int reject_reasons;
 	int progress = -1;
 
 	argv++;
@@ -223,7 +228,7 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 	ret |= finish_connect(conn);
 
 	if (!helper_status)
-		transport_print_push_status(dest, remote_refs, args.verbose, 0, &nonfastforward);
+		transport_print_push_status(dest, remote_refs, args.verbose, 0, &reject_reasons);
 
 	if (!args.dry_run && remote) {
 		struct ref *ref;
diff --git a/cache.h b/cache.h
index 843689b68..8f89f17a0 100644
--- a/cache.h
+++ b/cache.h
@@ -1003,14 +1003,19 @@ struct ref {
 	unsigned char old_sha1[20];
 	unsigned char new_sha1[20];
 	char *symref;
-	unsigned int force:1,
+	unsigned int
+		force:1,
+		requires_force:1,
 		merge:1,
 		nonfastforward:1,
+		not_forwardable:1,
+		update:1,
 		deletion:1;
 	enum {
 		REF_STATUS_NONE = 0,
 		REF_STATUS_OK,
 		REF_STATUS_REJECT_NONFASTFORWARD,
+		REF_STATUS_REJECT_ALREADY_EXISTS,
 		REF_STATUS_REJECT_NODELETE,
 		REF_STATUS_UPTODATE,
 		REF_STATUS_REMOTE_REJECT,
diff --git a/remote.c b/remote.c
index 6aa49c03d..225073909 100644
--- a/remote.c
+++ b/remote.c
@@ -1279,12 +1279,34 @@ int match_push_refs(struct ref *src, struct ref **dst,
 	return 0;
 }
 
+static inline int is_forwardable(struct ref* ref)
+{
+	struct object *o;
+
+	if (!prefixcmp(ref->name, "refs/tags/"))
+		return 0;
+
+	/* old object must be a commit */
+	o = parse_object(ref->old_sha1);
+	if (!o || o->type != OBJ_COMMIT)
+		return 0;
+
+	/* new object must be commit-ish */
+	o = deref_tag(parse_object(ref->new_sha1), NULL, 0);
+	if (!o || o->type != OBJ_COMMIT)
+		return 0;
+
+	return 1;
+}
+
 void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 	int force_update)
 {
 	struct ref *ref;
 
 	for (ref = remote_refs; ref; ref = ref->next) {
+		int force_ref_update = ref->force || force_update;
+
 		if (ref->peer_ref)
 			hashcpy(ref->new_sha1, ref->peer_ref->new_sha1);
 		else if (!send_mirror)
@@ -1297,34 +1319,55 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 			continue;
 		}
 
-		/* This part determines what can overwrite what.
-		 * The rules are:
+		/*
+		 * The below logic determines whether an individual
+		 * refspec A:B can be pushed.  The push will succeed
+		 * if any of the following are true:
 		 *
-		 * (0) you can always use --force or +A:B notation to
-		 *     selectively force individual ref pairs.
+		 * (1) the remote reference B does not exist
 		 *
-		 * (1) if the old thing does not exist, it is OK.
+		 * (2) the remote reference B is being removed (i.e.,
+		 *     pushing :B where no source is specified)
 		 *
-		 * (2) if you do not have the old thing, you are not allowed
-		 *     to overwrite it; you would not know what you are losing
-		 *     otherwise.
+		 * (3) the update meets all fast-forwarding criteria:
 		 *
-		 * (3) if both new and old are commit-ish, and new is a
-		 *     descendant of old, it is OK.
+		 *     (a) the destination is not under refs/tags/
+		 *     (b) the old is a commit
+		 *     (c) the new is a descendant of the old
 		 *
-		 * (4) regardless of all of the above, removing :B is
-		 *     always allowed.
+		 *     NOTE: We must actually have the old object in
+		 *     order to overwrite it in the remote reference,
+		 *     and the new object must be commit-ish.  These are
+		 *     implied by (b) and (c) respectively.
+		 *
+		 * (4) it is forced using the +A:B notation, or by
+		 *     passing the --force argument
 		 */
 
-		ref->nonfastforward =
-			!ref->deletion &&
-			!is_null_sha1(ref->old_sha1) &&
-			(!has_sha1_file(ref->old_sha1)
-			  || !ref_newer(ref->new_sha1, ref->old_sha1));
+		ref->not_forwardable = !is_forwardable(ref);
 
-		if (ref->nonfastforward && !ref->force && !force_update) {
-			ref->status = REF_STATUS_REJECT_NONFASTFORWARD;
-			continue;
+		ref->update =
+			!ref->deletion &&
+			!is_null_sha1(ref->old_sha1);
+
+		if (ref->update) {
+			ref->nonfastforward =
+				!has_sha1_file(ref->old_sha1)
+				  || !ref_newer(ref->new_sha1, ref->old_sha1);
+
+			if (ref->not_forwardable) {
+				ref->requires_force = 1;
+				if (!force_ref_update) {
+					ref->status = REF_STATUS_REJECT_ALREADY_EXISTS;
+					continue;
+				}
+			} else if (ref->nonfastforward) {
+				ref->requires_force = 1;
+				if (!force_ref_update) {
+					ref->status = REF_STATUS_REJECT_NONFASTFORWARD;
+					continue;
+				}
+			}
 		}
 	}
 }
diff --git a/send-pack.c b/send-pack.c
index f50dfd9f4..1c375f0a2 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -229,6 +229,7 @@ int send_pack(struct send_pack_args *args,
 		/* Check for statuses set by set_ref_status_for_push() */
 		switch (ref->status) {
 		case REF_STATUS_REJECT_NONFASTFORWARD:
+		case REF_STATUS_REJECT_ALREADY_EXISTS:
 		case REF_STATUS_UPTODATE:
 			continue;
 		default:
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index b5417cc95..60093728f 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -368,7 +368,7 @@ test_expect_success 'push with colon-less refspec (2)' '
 		git branch -D frotz
 	fi &&
 	git tag -f frotz &&
-	git push testrepo frotz &&
+	git push -f testrepo frotz &&
 	check_push_result $the_commit tags/frotz &&
 	check_push_result $the_first_commit heads/frotz
 
@@ -929,6 +929,48 @@ test_expect_success 'push into aliased refs (inconsistent)' '
 	)
 '
 
+test_expect_success 'push requires --force to update lightweight tag' '
+	mk_test heads/master &&
+	mk_child child1 &&
+	mk_child child2 &&
+	(
+		cd child1 &&
+		git tag Tag &&
+		git push ../child2 Tag &&
+		git push ../child2 Tag &&
+		>file1 &&
+		git add file1 &&
+		git commit -m "file1" &&
+		git tag -f Tag &&
+		test_must_fail git push ../child2 Tag &&
+		git push --force ../child2 Tag &&
+		git tag -f Tag &&
+		test_must_fail git push ../child2 Tag HEAD~ &&
+		git push --force ../child2 Tag
+	)
+'
+
+test_expect_success 'push requires --force to update annotated tag' '
+	mk_test heads/master &&
+	mk_child child1 &&
+	mk_child child2 &&
+	(
+		cd child1 &&
+		git tag -a -m "message 1" Tag &&
+		git push ../child2 Tag:refs/tmp/Tag &&
+		git push ../child2 Tag:refs/tmp/Tag &&
+		>file1 &&
+		git add file1 &&
+		git commit -m "file1" &&
+		git tag -f -a -m "message 2" Tag &&
+		test_must_fail git push ../child2 Tag:refs/tmp/Tag &&
+		git push --force ../child2 Tag:refs/tmp/Tag &&
+		git tag -f -a -m "message 3" Tag HEAD~ &&
+		test_must_fail git push ../child2 Tag:refs/tmp/Tag &&
+		git push --force ../child2 Tag:refs/tmp/Tag
+	)
+'
+
 test_expect_success 'push --porcelain' '
 	mk_empty &&
 	echo >.git/foo  "To testrepo" &&
diff --git a/transport-helper.c b/transport-helper.c
index 4713b6930..965b778cb 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -661,6 +661,11 @@ static void push_update_ref_status(struct strbuf *buf,
 			free(msg);
 			msg = NULL;
 		}
+		else if (!strcmp(msg, "already exists")) {
+			status = REF_STATUS_REJECT_ALREADY_EXISTS;
+			free(msg);
+			msg = NULL;
+		}
 	}
 
 	if (*ref)
@@ -720,6 +725,7 @@ static int push_refs_with_push(struct transport *transport,
 		/* Check for statuses set by set_ref_status_for_push() */
 		switch (ref->status) {
 		case REF_STATUS_REJECT_NONFASTFORWARD:
+		case REF_STATUS_REJECT_ALREADY_EXISTS:
 		case REF_STATUS_UPTODATE:
 			continue;
 		default:
diff --git a/transport.c b/transport.c
index 9932f402d..2673d273f 100644
--- a/transport.c
+++ b/transport.c
@@ -659,7 +659,7 @@ static void print_ok_ref_status(struct ref *ref, int porcelain)
 		const char *msg;
 
 		strcpy(quickref, status_abbrev(ref->old_sha1));
-		if (ref->nonfastforward) {
+		if (ref->requires_force) {
 			strcat(quickref, "...");
 			type = '+';
 			msg = "forced update";
@@ -695,6 +695,10 @@ static int print_one_push_status(struct ref *ref, const char *dest, int count, i
 		print_ref_status('!', "[rejected]", ref, ref->peer_ref,
 						 "non-fast-forward", porcelain);
 		break;
+	case REF_STATUS_REJECT_ALREADY_EXISTS:
+		print_ref_status('!', "[rejected]", ref, ref->peer_ref,
+						 "already exists", porcelain);
+		break;
 	case REF_STATUS_REMOTE_REJECT:
 		print_ref_status('!', "[remote rejected]", ref,
 						 ref->deletion ? NULL : ref->peer_ref,
@@ -714,7 +718,7 @@ static int print_one_push_status(struct ref *ref, const char *dest, int count, i
 }
 
 void transport_print_push_status(const char *dest, struct ref *refs,
-				  int verbose, int porcelain, int *nonfastforward)
+				  int verbose, int porcelain, unsigned int *reject_reasons)
 {
 	struct ref *ref;
 	int n = 0;
@@ -733,18 +737,19 @@ void transport_print_push_status(const char *dest, struct ref *refs,
 		if (ref->status == REF_STATUS_OK)
 			n += print_one_push_status(ref, dest, n, porcelain);
 
-	*nonfastforward = 0;
+	*reject_reasons = 0;
 	for (ref = refs; ref; ref = ref->next) {
 		if (ref->status != REF_STATUS_NONE &&
 		    ref->status != REF_STATUS_UPTODATE &&
 		    ref->status != REF_STATUS_OK)
 			n += print_one_push_status(ref, dest, n, porcelain);
-		if (ref->status == REF_STATUS_REJECT_NONFASTFORWARD &&
-		    *nonfastforward != NON_FF_HEAD) {
+		if (ref->status == REF_STATUS_REJECT_NONFASTFORWARD) {
 			if (!strcmp(head, ref->name))
-				*nonfastforward = NON_FF_HEAD;
+				*reject_reasons |= REJECT_NON_FF_HEAD;
 			else
-				*nonfastforward = NON_FF_OTHER;
+				*reject_reasons |= REJECT_NON_FF_OTHER;
+		} else if (ref->status == REF_STATUS_REJECT_ALREADY_EXISTS) {
+			*reject_reasons |= REJECT_ALREADY_EXISTS;
 		}
 	}
 }
@@ -1031,9 +1036,9 @@ static void die_with_unpushed_submodules(struct string_list *needs_pushing)
 
 int transport_push(struct transport *transport,
 		   int refspec_nr, const char **refspec, int flags,
-		   int *nonfastforward)
+		   unsigned int *reject_reasons)
 {
-	*nonfastforward = 0;
+	*reject_reasons = 0;
 	transport_verify_remote_names(refspec_nr, refspec);
 
 	if (transport->push) {
@@ -1099,7 +1104,7 @@ int transport_push(struct transport *transport,
 		if (!quiet || err)
 			transport_print_push_status(transport->url, remote_refs,
 					verbose | porcelain, porcelain,
-					nonfastforward);
+					reject_reasons);
 
 		if (flags & TRANSPORT_PUSH_SET_UPSTREAM)
 			set_upstreams(transport, remote_refs, pretend);
diff --git a/transport.h b/transport.h
index 4a61c0c3f..bfd2df582 100644
--- a/transport.h
+++ b/transport.h
@@ -140,11 +140,13 @@ int transport_set_option(struct transport *transport, const char *name,
 void transport_set_verbosity(struct transport *transport, int verbosity,
 	int force_progress);
 
-#define NON_FF_HEAD 1
-#define NON_FF_OTHER 2
+#define REJECT_NON_FF_HEAD     0x01
+#define REJECT_NON_FF_OTHER    0x02
+#define REJECT_ALREADY_EXISTS  0x04
+
 int transport_push(struct transport *connection,
 		   int refspec_nr, const char **refspec, int flags,
-		   int * nonfastforward);
+		   unsigned int * reject_reasons);
 
 const struct ref *transport_get_remote_refs(struct transport *transport);
 
@@ -170,7 +172,7 @@ void transport_update_tracking_ref(struct remote *remote, struct ref *ref, int v
 int transport_refs_pushed(struct ref *ref);
 
 void transport_print_push_status(const char *dest, struct ref *refs,
-		  int verbose, int porcelain, int *nonfastforward);
+		  int verbose, int porcelain, unsigned int *reject_reasons);
 
 typedef void alternate_ref_fn(const struct ref *, void *);
 extern void for_each_alternate_ref(alternate_ref_fn, void *);